Opto-electronic digital memory cells are characterized by thin film storage media (less than 10 μm thick), rapid response times, high charge storage density, virtually unlimited information storage times, and low operating voltages (0.5 to 10 V).
There are approaches to use optoelectronic elements on a flexible substrate, e.g., on a polymer layer, with organic metalloporphyrins (e.g. ZnODEP) in the form of a self-assembled mono layer as active layer. Memory cells known up to now and based on the Zn-porphyrine complexes comprise a transparent top electrode. The most common transparent electrode is made up of a so-called InSnO-Indium Tin Oxide material (ITO), since this material has high electrical conductivity. The manufacturing of a top electrode made up of an ITO material, has usually been done by deposited the material by the way of sputtering the ITO targets on the active layer.
Some memory cells, which are related to the present invention, are described in C. Li, H. Pan, A. J. Bard, M. A. Fox, U.S. Pat. No. 5,327,373,and C. Li, A. J. Bard, Acc Chem. Res. Vol. 32,(1999), p. 235. The above-mentioned documents are incorporated by reference.
The sputtered atoms In, Sn and O have considerable kinetic energies which enable a certain number of atoms to penetrate molecular self-assembled monolayers, where they can be incorporated directly or after several relaxation processes into the organic porphyrin molecule of the active layer. While the incorporation of oxygen onto the borders of the pyroll rings of the ZnODEP molecule results in only minor disruptions, the incorporation or the chemical arranging of In or Sn atoms means a disruption of the memory effect in the Zn-porphyrin molecule. If indium or tin replaces the Zn-cation at the centrally functional place of the memory molecule, then the memory function of such a cell is destroyed, since the memory effect of the Zn-porphyrine based redox center has been disrupted.